Electrolytic condenser



April 1930. s. T. wobDHuLL 1,753,912

ELECTROLYTIC CONDENSER Filed Sept. 28, 1926 Patented Apr. 8, 1930- UNITED s'ravrssv PATENT OFFICE mom. '1'. woommrm, or wmcnssrna, mssacnusm'rs, nssrenon Torin: mm

coarom-rron, or mnmronn, uassacnnsnrrsn coaromrron or 0310 mornomzrrc .comamrsnn Application. filed September as, 1926. Serial no. name."

The present inventionrelates to electrolytic condensers.

The objects of the present invention are to provide a durable and easily assembled electrolytic condenser, and also to provide a selfcontained electrolytic condenser unit including a plurality of associated capacitances and adapted particularly for use in filter circuits. The usual filter circuit, particularly one employed for smoothing rectified alternating current, employs a plurality of series choke coils in combination with condensers connected across the line. According to the present invention, the condensers are of the electrolytic type and are included in a single unit which comprises a plurality of anodes immersed in a single electrolyte in which is immersed a single cathode. In the electrolytic condenser, the anodes consist of filming electrodes which are provided with a thin film of dielectric material. This film resists electrical conduction from the filming electrode to the electrolyte but permits conduction in the reverse direction. For a successful condenser, therefore, it is essential that the filming electrode be maintained at a positive potential so as to prevent a reverse conduction current, which would result in a partial destruction of the film. While there is no tendency toward reverse conduction between cathode and anode in a filter circuit, it will be seen that the introduction of all of the condenser units into one electrolyte gives riseto a possibility of reverse conduction between one or more of the anodes because of potential differences between points in the rectified supply line to which the anodes are connected. This is particularly true in the case of plate voltage supply units for radio receivers in which both high and low voltages are supplied for operation of amplifier and detector tubes respectively, the potential difference which exists between the high and low voltage terminals of the apparatus serving to impress on the condenser anodes a potential which may tend to result in a reverse conduction.

According to a feature of'the present invention, means are provided for shielding 60 the anodes from each other so that the paths for electrical conduction between filter sectlons throu h the electrolyte are intercepted. Thls shieldlng is preferably arranged to be placed between anodes which are maintained I I at a considerable potential difierence.

Another feature of the present invention contemplates the provision of means for accurately positioningthe electrodes and maintaining them against turning either during assembly or in subsequent use. The filming electrodes are mounted on frames which are f also of filming material such as aluminum. In the present constructlon, means are associated with the support on which the electrode assemblies are mounted for preventing displacement of the electrodes, thus avoiding breakage or distortion of the necessarily fragile material of which the filming electrodes are composed.

In the accompanying drawings, Fig. 1 is a plan view of a condenser unit embodying the features of the present invention; Fig. 2 is a horizontal view in section taken on line 22 of Fig. 3 showing the electrode construction of the condenser unit; Fig. 3 is a section on line 3-3 of Fig. 1 and Fig. 4 is a diagrammatic view of a filter or smoothing circuit in which the condenser is adapted to be used.

The invention is herein shown and described as embodied in a filter circuit adapted to be used in connection with a rectifying device for supplying plate current to radio receivers from an alternating current source.

The condenser comprises a container 5 adapted to receive a suitable electrolyte in whlch is immersed a plurality of filming electrodes indicated at 6, 8 and 10, and a non-filming electrode12. The electrodes 6 and 8 are of large size and the central electrode 10 is of relatively smaller size and is arranged between the electrodes 6 and 8. The filming electrodes are of aluminum and the non-filming electrode is of nickel, the electrolyte preferably consisting of borax and boric acid. The filming electrodes are adapted to be con-v nected to the positive side of the circuit and must be maintained under a positive potential with respect to the non-filmingelectrode to insure maintenance of the film, which is necessary for the condenser action. The filming electrodes consist of thinsheets provided with a large number of folds 14 to afford an extended surface. Each of the electrodes 6 and 8 is supported on a frame 16, also of filming material, which is of hollow rectangular construction and supported by bolts 17 from a cover plate 18 which is seated on the container. The ends of the electrode sheet are firmly secured to the supporting members by ears '20 which are struck up from the latter and bent into firm engagement with the sheet and welded thereto. Theelectrode 10 is Slmllarly attached to a strip 21 which is also secured to the cover. The entire filming electrode assembly is provided with a film of d1- electric material, according to any preferred method. The cover plate is of insulatingmaterial, preferably porcelain, and is provided with a pair of positioning lugs 22, one of.

which is arranged between the electrodes 6 and 10 and the other between the electrodes 8 and 10. The lugs are spaced to engage with the frames to position the latter and prevent turning or distorting thereof during assembly or in subsequent use. Each lug 1s recessed at 23 to accommodate washers 24 which surround the bolts to prevent evaporation through the openings of the cover. The nonfilming electrode 12 is secured to posts 25 bolted to the cover. This electrode is in the form of a shield completely surrounding and enclosing the central electrode 10 to shield the latter from electrical conduction between it and either of the other filming electrodes. The shield extends above the level of the electrolyte and to a level below the bottom of the supporting frame of the non-filming electrode so as to lntercept any posslble paths for electrical conduction between the anodes. A terminal or soldering lug 26 is associated with each electrode.

A circuit in which the condenser unit is adapted to be used is shown in Fig. 3 and includes a transformer 30, the primary of which is connected to an alternating current supply and the secondary to a rectifier tube illustrated diagrammatically at 32, which is constructed to give full wave rectification. The center of the secondary is tapped for the negative lead 34 of the filter system. The filter system includes a pair of series chokes 36 in series with the positive lead from the rectifier tube. Directly across the line ahead of the first choke is connected a small condenser 38 which may be of the usual paper or mica construction, a large capacity being unnecessary for the condenser at this place. The cathode or filming electrode of the electrolytic unit is connected to the negative lead while the anodes 6 and 8 are connected to points immediately following the respective chokes 36. The voltage available between the positive and negative leads is a high voltage suitable for energizing the plates of the amplifier tubes of a radio receiver, a terminal B+ being employed to afford connection to the receiver. To obtain a plate voltage for the detector, a terminal D+ is provided, which is connected to the B+ lead through a resistance 40. The anode 10 of the electrolytic unit is connected to the D+ lead. The negative lead 34.- is provided with a terminal B- for connection to the receiver in the usual manner.

It will be seen that electrode 10 is completely shielded from reverse conduction with respect to the two anodes 6 and 8, while the latter are effectively, if not completely, shielded from each other by provision of the cathode between them.

Inasmuch as 'the voltage drop through either of the chokes is not large, there Wlll I not be a large difference of potential between the anodes 6 and 8 of the electrolytic condenser unit. However, the voltage between the anode 10 and the other anodes of the unit is determined by the difference between the voltage desirable for the amplifier and for the detector of the receiver and might be sufficient, if it were not for the shield 22, to impair the operation of the condenser. It will be appreciated that the flow of current, if any should be established, would be from the anode 6 or 8 to the anode 10. While the film on the anodes 6 and 8 tends to oppose a very large resistance to direct conduction of cur-. rent, there will nevertheless be a tendency for a charging current to flow, due to the fact that the potentials impressed on the terminals of the condensers are not direct currents but fluctuate somewhat in value because of the nature of the rectified current delivered from the tube 32. The flow of this current to the anode 10 would be in such a direction as to tend to destroy the film on this anode, thus permitting direct conduction from the electrolyte to the anode. Such action, however, is prevented by the shield 22 which intercepts all possible paths of electrical conduction extending from the anodes 6 and 8 toward the anode 10. The only possible paths for flow of electric current through the electrolyte, therefore, are those which terminate on the cathode 12 or its associated shield 22. The shield, moreover, prevents the establishment of electrical potential stresses which, even though unaccompanied by actual flow of conduction current, might be of suflicient magnitude to cause damage to the anode films.

Another important advantage resulting from the present invention resides in the substantially complete elimination of pulsations in the output of the filter. If the shielding means were not present, some hum might be introduced by the flow through the resistance of the electrolyte of the imperfectly filtered current of the first condenser section of the filter. For example, a pulsating charging current flows into the anode 6 through the anode film by condenser action and thence through the electrolyte to the negative electrode. The entire body of electrolyte in reality forms the cathode. Since the electrolyte has some resistance, the flow of alternating current through it would give rise to an alternating voltage drop which would also be impressed on the circuits of the final filter sections. By the provision of shielding, however, the entire body of electrolyte does not form a common cathode for all of the sections. That is to say, the electrolyte is'in effect divided into isolated portions associated with the different anodes. Thus, there are no common resistances through which an alternating current may flow to impress an alternating potential on the final filter sections. For example, the pulsating current of the anode 6 passes through the shortest electrolyte path to the negative electrode shield 12. Similarly, the aths of current conduction for the other filter sections are through short paths of the electrolyte not in common to the path of current .in the first filter section.

What is claimed is:

1. An electrolytic condenser having an electrolyte, a cathode electrode, a plurality of filming-anodes immersed in the electrolyte and adapted to be placed at different electrical potentials, and means for shielding from each other anodes which are maintained at Widely varying potentials.

2. An electrolytic condenser having an electrolyte, a cathode electrode, a plurality of filming anodes immersed in the electrolyte and adapted to be placed at different electrical potentials, and means connected with the cathode and extending through the elec-. trolyte for shielding from each other anodes which are maintained at widely varying potentials,

3. An electrolytic condenser having an electrolyte, a cathode electrode, a plurality of filmmg anodes immersed in the electrolyte and adapted tobe placed at different electrical potentials, and a conductin shield connected with the cathode electr e and partially surrounding one of the anodes to protect it from electrical stresses with respect to other anodes maintained at a widely varying potential.

4. An electrolytic condenser comprising a container, filmin and-non-filming electrodes, frames to which the filming electrodes are attached, an insulating cover for the.

container having dependin s aced lugs against thesides of which t e ing electrode frames are adapted to engage, means for securing the frames to the cover while positionin them a ainst the lugs, and a support .for t e non-filming electrode.

' 5. An electrolytic condenser com risin an electrolyte, a negative electrode and two ing anodes immersed in the electrolyte, the

filming anodes being adapted to be maintained at different electrical potential differences with respect to the negative electrode, the negative electrode comprising a conducting member surrounding one of the anodes to shield it from the other anode.

6. An electrolytic condenser comprising a container, an electrolyte, a plurality of filmin anodes immersed in the electrolyte and adapted to form difi'erent sections of a filter, a negative electrode, and means for isolating the portions of the electrolyte associated with the several anodes from each other to prevent electrical conduction of currents of difierent filter sections through common portions of the electrolyte.

7. An electrolytic condenser comprising a container, an electrolyte, a plurality of filming anodes immersed in the electrolyte and adapted to form difi'erent sections of a filter a negative terminal, and shielding means of conducting material connected to the negative'terminal and isolating portions of the electrolyte associated with the several electrodes from each other to prevent electrical conduction of currents of diflerent filter sections through common portions of the electrolyte. 1

8. An electrolytic condenser comprising a container, an electrolyte, a plurality of filming anodes adapted to form difli'erent sections of a filter and immersed in the electrolyte, a negative terminal, and shielding connected with the negative terminal and im mersed in the electrolyte and extending above the level of the electrolyte for shielding the difi'erent anodes from each other.

9. An electrolytic condenser comprisin an electrolyte, two filmin anodes immerse in the electrolyte, the lming anodes being adapted to form different sections of a filter, a negative terminal and a conducting shield connected with the negative terminal and surrounding one of the anodes and extendin above the level of the electrolyte to shiel the anodes from each other.

In testimony whereof I have signed my name to this s ecific'ation. V

S MUEL T. WOODHULL. 

